2016 Update

Task/Combinations/AppleScript/combinations-1.applescript

@@ -1,27 +1,27 @@
 on comb(n, k)
-	set c to {}
-	repeat with i from 1 to k
-		set end of c to i's contents
-	end repeat
-	set r to {c's contents}
-	repeat while my next_comb(c, k, n)
-		set end of r to c's contents
-	end repeat
-	return r
+    set c to {}
+    repeat with i from 1 to k
+        set end of c to i's contents
+    end repeat
+    set r to {c's contents}
+    repeat while my next_comb(c, k, n)
+        set end of r to c's contents
+    end repeat
+    return r
 end comb
 
 on next_comb(c, k, n)
-	set i to k
-	set c's item i to (c's item i) + 1
-	repeat while (i > 1 and c's item i ≥ n - k + 1 + i)
-		set i to i - 1
-		set c's item i to (c's item i) + 1
-	end repeat
-	if (c's item 1 > n - k + 1) then return false	
-	repeat with i from i + 1 to k
-		set c's item i to (c's item (i - 1)) + 1
-	end repeat
-	return true
+    set i to k
+    set c's item i to (c's item i) + 1
+    repeat while (i > 1 and c's item i ≥ n - k + 1 + i)
+        set i to i - 1
+        set c's item i to (c's item i) + 1
+    end repeat
+    if (c's item 1 > n - k + 1) then return false
+    repeat with i from i + 1 to k
+        set c's item i to (c's item (i - 1)) + 1
+    end repeat
+    return true
 end next_comb
 
 return comb(5, 3)

Task/Combinations/AppleScript/combinations-3.applescript

@@ -0,0 +1,104 @@
+-- comb :: Int -> [a] -> [[a]]
+on comb(n, lst)
+    set h to head(lst)
+
+    script headPrepended
+        on lambda(t)
+            h & t
+        end lambda
+    end script
+
+    if n < 1 then
+        [[]]
+    else if length of lst = 0 then
+        []
+    else
+        set xs to tail(lst)
+
+        map(headPrepended, ¬
+            comb(n - 1, xs)) & comb(n, xs)
+    end if
+end comb
+
+
+-- TEST
+
+-- spaced :: [a] -> String
+on spaced(lst)
+    intercalate(space, lst)
+end spaced
+
+on run
+
+    intercalate(linefeed, ¬
+        map(spaced, comb(3, range(0, 4))))
+
+end run
+
+
+
+-- GENERIC FUNCTIONS
+
+-- map :: (a -> b) -> [a] -> [b]
+on map(f, xs)
+    tell mReturn(f)
+        set lng to length of xs
+        set lst to {}
+        repeat with i from 1 to lng
+            set end of lst to lambda(item i of xs, i, xs)
+        end repeat
+        return lst
+    end tell
+end map
+
+-- Lift 2nd class handler function into 1st class script wrapper
+-- mReturn :: Handler -> Script
+on mReturn(f)
+    if class of f is script then
+        f
+    else
+        script
+            property lambda : f
+        end script
+    end if
+end mReturn
+
+-- intercalate :: Text -> [Text] -> Text
+on intercalate(strText, lstText)
+    set {dlm, my text item delimiters} to {my text item delimiters, strText}
+    set strJoined to lstText as text
+    set my text item delimiters to dlm
+    return strJoined
+end intercalate
+
+-- range :: Int -> Int -> [Int]
+on range(m, n)
+    if n < m then
+        set d to -1
+    else
+        set d to 1
+    end if
+    set lst to {}
+    repeat with i from m to n by d
+        set end of lst to i
+    end repeat
+    return lst
+end range
+
+-- head :: [a] -> a
+on head(xs)
+    if length of xs > 0 then
+        item 1 of xs
+    else
+        missing value
+    end if
+end head
+
+-- tail :: [a] -> [a]
+on tail(xs)
+    if length of xs > 1 then
+        items 2 thru -1 of xs
+    else
+        {}
+    end if
+end tail

Task/Combinations/AppleScript/combinations.applescript

@@ -1,27 +0,0 @@
-on comb(n, k)
-	set c to {}
-	repeat with i from 1 to k
-		set end of c to i's contents
-	end repeat
-	set r to {c's contents}
-	repeat while my next_comb(c, k, n)
-		set end of r to c's contents
-	end repeat
-	return r
-end comb
-
-on next_comb(c, k, n)
-	set i to k
-	set c's item i to (c's item i) + 1
-	repeat while (i > 1 and c's item i ≥ n - k + 1 + i)
-		set i to i - 1
-		set c's item i to (c's item i) + 1
-	end repeat
-	if (c's item 1 > n - k + 1) then return false	
-	repeat with i from i + 1 to k
-		set c's item i to (c's item (i - 1)) + 1
-	end repeat
-	return true
-end next_comb
-
-return comb(5, 3)